Thankfully, I quickly found a workaround for the (second) SPI bug I complained about last time, so now I have a working setup with both a display and SD card!

That means I can now _really_ write code on the laptop it self - being able to save to the SD card is very useful - and I managed to hack up a passable version of Snake pretty quickly. No (other) computer involved, programmed exclusively on the PotatoP, using the built-in documentation in the latest version of uLisp for reference! I even hooked up a little speaker to some GPIO pins to make some clicks and bleeps for the game.

The size of the screen is surprisingly OK, the text is very clearly readable at the default 5x7 font size as long as there is decent light. And 53 characters is wide enough that it seems I can get used to it - I should refactor my code into smaller units anyway :-). The editor is still a bit slow when editing more than a screenful of text, but moving to a better data structure than "just a big string" is likely to help.

I also splurged on a few more items; most importantly a Nordic Semiconductor Power Profiler Kit II. I've also received another solar controller board by Jasper Sikken, this one using supercapacitors instead of a battery for energy storage. I really want to see if I can make this work well enough instead of a battery, as it has a lot of advantages - such as no toxic materials or worries about degrading battery chemistry.

Of course I had to unpack and test the power profiler - and wow, this is certainly much better than trying to peep at a multimeter. As I suspected there are some current  spikes, and it quickly becomes clear that there is still much room for improvement, but it's not as bad as I feared. power use at "idle" in the editor or uLisp REPL is currently at 2.64mW, and while running uLisp code to draw a fractal while updating the screen, it's 5mW.

Unfortunately, even when at idle, holding down all the arrow keys makes power jump up to 16.4 mW. So surprisingly, the greatest source of power consumption is the keyboard scanning - hopefully due to some simple-to-fix misconfiguration of the GPIO. My no-name second hand SD card also sucks down another 30mW once it's been initialized, but according to the datasheet the one I have ordered from Adafruit should do a lot better. So I still have hope to get the active power consumption below 6mW, and much closer to 0 at idle, once I get all that worked out.

Some concessions to usability must come first though - I need to redesign the editor to handle larger files, as well as add some very basic features like key repeat, faster scrolling, selecting text, copy/paste and so on. My library of lisp functions and little toys and experiments is growing quickly and is becoming unmanageable with the current version!